The first three have long been classed together under the name of noble or perfect metals, and the remaining ones have been associated with them as they have been respectively discovered. Nickel, which was for some time placed among the imperfect metals, was removed a few years since into this class, after a more accurate investigation of its relation to oxygen.'

590. Dr. Murray introduces his account of individual metals in the following words: The class of metals has been subdivided into orders, under which the individual metals are arranged. Gold, silver, and platina, preserving their lustre on exposure to the air, possessing a high degree of ductility and malleability, and not being oxidated when exposed to a high heat, have been placed in one order, under the appellation of perfect or noble metals. Quicksilver, copper, iron, tin, and lead, possessing ductility and malleability, but being oxidated by heat, have been placed together under the name of imperfect metals. The others, zinc, antimony, bismuth, cobalt, nickel, manganese, arsenic, (and the greater number of the newly-discovered metals, may be added to this order), having little ductility or malleability, were termed semi-metals. This was the old division, others have been in

troduced; but any classification of this kind is inaccurate; no advantage is gained by forming such orders, and they are altogether artificial; each metal forms a species, and they may be considered individually in that order in which the transition is most natural, beginning with those which have the characteristic metallic properties, tenacity and specific gravity, in the highest degree. Those of recent discovery, and which are only imperfectly investigated, may be placed after the others.'

591. It will be obvious to the reader upon what principle we have thus laid before him the remarks of some of our best authors, on the subject of metallic classification; the very discussion involves matter of much interest, inasmuch as, if duly attended to, information will be found in it respecting the habits of the several metals, in reference to combustibility, acidifiability, if we may so express it, and other particulars. We now proceed, as it was above intimated we should, to follow the order of Dr. Ure, on account of its appearing to us to unite in some measure the natural with the chemical schemes of arrangement; and therefore to effect the purpose of assisting the conception and the recognition of modern discoveries, without violating the order in which it was the custom to treat of metallic substances, prior to the important revolutions in the doctrines and principles of chemistry.

592. It is right to say, that, in many instances at least, the habits, &c. of the metals will be discussed less in detail than might be expected in a treatise on chemistry, on account of notices which it is found necessary to take of them in the alphabetical arrangement of our work.

PLATINUM.

593. This is a metal of modern discovery. It is met with in South America; but is mixed with several other substances when it reaches this country; the pure metal may be obtained by dissolving the ore in nitro-muriatic acid, and then adding a solution of muriate of ammonia.

594. Platinum is white, somewhat resembling silver in color, but heavier by far; and it is exceedingly ductile, tenacious, and malleable. It is extremely difficult of fusion. Under the blow-pipe, however, with oxygen gas, it may be melted. It is a very slow conductor of heat; its expansibility by heat is less than that of steel. Like iron it may be welded. Its oxides are only procurable by a circuitous process; it is said to be oxidifiable in three proportions, viz. about 8, 12, and 16 to 100 of the metal. But the subject, says Dr. Henry, requires more accurate investigation before we can assign with any confidence its equivalent number.

595. The metal is acted on by nitro-muriatic acid, as above stated, and by chlorine. Chloride of platinum is to be obtained by evaporating the solution in the nitro-muriatic acid; then heating the product to whiteness, by which process chlorine gas will be evolved. The dry compound is a chloride of platinum, which may be crystallised by careful management; it has the property of being precipitated by a solution of muriate of

ammonia, which is almost peculiar to, or characteristic of, platinum. The chloride of platinum is, however, decomposed by ether.

596. Sulphuret of platinum.-This may be obtained by decomposing the chloride with sulphureted hydrogen, but it is not easy to ascertain the precise composition of the sulphuret, since the sulphur of it is so soon converted into sulphuric acid. There are, according to Mr. Edmund Davy, two other ways of forming the sulphuret: first, by heating the metal finely divided with sulphur; and the second by heating three parts of the ammonia muriate of platinum with two of sulphur.

597. The sulphate of platinum is best procured by acting on the sulphuret with nitric acid. The action of alcohol on this substance (the sulphate) occasions the formation of a substance which is possessed of very singular properties (Philosophical Transactions, 1820). Equal volumes of a strong aqueous solution of this sulphate and of alcohol, heated together, deposit a black powder, which, after being well edulcorated, and dried at a very gentle heat, exhibits the following properties

598. It is black, and in small lumps, which are soft to the touch, and easily reduced to an impalpable powder. This powder is tasteless, and insoluble in water, either hot or cold. When gently heated on a slip of platinum, a feeble explosion takes place, accompanied with a hissing noise, and a flash of red light, and the platinum is reduced. Brought into contact with ammoniacal gas, it becomes red-hot and scintillates. It is instantly decomposed by alcohol, as is shown in a very striking manner, by moistening paper, sand, cork, or sponge, with that fluid, and placing the smallest particle of the powder on them. It hisses, and becomes red-hot; and Mr. E. Davy, to whom we owe its discovery, proposes it as an excellent means of kindling a match. It appears to consist of 961 per cent. platinum, with nitrous acid, a little oxygen, and a very minute proportion of carbon. The nitrous acid is accounted for by the peculiar way in which the sulphate had been formed. Henry.

599. Phosphuret of platinum is to be formed either by passing phosphureted hydrogen into a solution of the metal, or by heating phosphorus with it in exhausted tubes. Phosphuret of platinum is a powder of a grayish blue appearance; it is infusible, and is said to contain 17 to the 100 of phosphurus.

600. A fulminating platinum may be formed by precipitating a solution of platinum with a slight excess of pure ammonia. The precipitate is to be boiled in potassa nearly to dryness, and when well washed and dried is the fulminating platinum; it seems to be a compound of oxide of platinum, ammonia, and water. It explodes at about 420° with a very loud report. Percussion will not cause it to explode.

601 The alloys of platinum have not been

applied to use. Roll up together a piece of platinum foil with a piece of lead foil of equal dimensions, and cautiously direct the flame of a candle by a blow-pipe towards the edges of this roll, and you will occasion an explosive combination of the two metals, the ignited particles emitting light in great quantities, and with a beautiful appearance. The same effect will be produced by a small piece of tin or antimony, or zinc rolled in platina leaf, and heated in the same manner. By combining seven parts of platinum with sixteen of copper, and of zinc, Mr. Cooper obtained a mixture much resembling gold.' Journal of Science and Arts, iii. p. 119.

For the specific gravity of this and of all the metals the table may be consulted.

GOLD.

602. This metal is found in a native state, mixed with a little silver or copper. Its color is various shades of yellow; its forms are massive, ramose, and crystallised in cubes and octahedra. The veins of gold are confined to primitive countries, but large quantities of this metal are collected in alluvial soils and in the beds of certain rivers, more especially those of the west coast of Africa and of Peru, Brasil, and Mexico. In Europe the streams of Hungary and Transylvania have afforded a respectable quantity of gold; it has been found also in the Rhine, the Rhone, and the Danube. Small quantities have been collected in Cornwall, and in the county of Wicklow in Ireland. Brande.

603. To obtain it in a state of purity standard gold must be dissolved in nitro-muriatic acid; one part by weight of the metal to three of the acid; the solution must be evaporated to dryness by a gentle heat, the dry mass re-dissolved in distilled water, and a solution then added to it of green sulphate of iron, which will precipitate the gold in a state of fine powder, which, after being washed with diluted nitric acid, and then with distilled water, may be fused.

604. Pure gold is of a deep yellow color. It has very considerable lustre; it may be melted at a moderate heat, and after fusion it crystallises. Its malleability and ductility have already been remarked upon. See the general characters of metals.

605. It is not oxidifiable by mere exposure to heat; but a powerful electric or galvanic impulse will bring it to the condition of a purple oxide.

606. The solvents of this metal are the nitromuriatic acid, and chlorine. When gold, in a state of minute division, is heated in chlorine a compound of a deep yellow color results, which is said to consist of 97 gold + 33.5 chlorine When acted upon by water a muriate of gold produced. Brande.

607. According to Pelletier there are two chlorides of gold.

Metal.

609. If this, says Mr. Brande, be considered a compoundofone proportional gold and one iodine, the number 228 must be adopted as the representative of gold, for 34: 66:: 1177; 228.3; anumber so much at variance with that deduced from other experiments, as to show the necessity of further enquiries, before either be adopted.

610. Oxides of this metal may be obtained by precipitating chloride of gold with magnesia, or potash.

611. From a solution of the metal in nitromuriatic acid, a solution of pure ammonia also precipitates an oxide of gold, and a portion of the ammonia combining with the oxide forms fulminating gold. This upon being heated detonates violently, the ammonia of it being decomposed by the increased temperature, its hydrogen uniting with the oxygen of the oxide, and nitrogen gas being liberated in a state of high expansion. The gold by this process is reduced to its me

tallic state.

612. Several combustible bodies will decompose chloride of gold in solution, and the metal in this case also is reduced to its metallic state; here the combustible materials seem to act by furnishing hydrogen to the chlorine.

613. Gold is precipitated from its solvent by ether, but the oxide of gold is instantly re-dissolved by the ether, and forms the etherial solution of gold. This solution is advantageously applied to the gilding of steel, scissars, lancets, and other instruments which it protects from rust with a very small expenditure of gold. Henry.

614. Gold will unite with sulphur into a sulphuret, by passing a current of sulphureted hydrogen through an aqueous solution of muriate of gold. The sulphuret falls down in the form of a black precipitate.

615. With phosphorus, also, gold will combine into a phosphuret, by heating gold leaf with phosphorus in a tube deprived of air. This has a gray color, and a metallic lustre.

616. For the methods of purifying gold by the operations of cupelling and quartation, the reader may consult Aikin's Chemical Dictionary, article Gold.

617. Gold, which is too soft in its pure state for many purposes, has its hardness greatly increased by being melted or alloyed with a small proportion of copper. It is a singular fact that some kinds of copper, which do not themselves appear defective in any respect, totally destroy the ductility of gold. This appears to be owing to the contamination of the copper with a very small quantity of lead and antimony, of either of which metals only about th in weight is sufficient to produce this injurious effect. Henry.

VOL. V.

618. Mercury and gold combine with great ease, and produce a white amalgam much used in gilding. For this purpose the amalgam is applied to the surface of the silver, the mercury is then driven off by heat, and the gold remains adhering to the silver, and is burnished. This process is called water gilding.

619. In gilding porcelain, gold powder is generally employed, obtained by the decomposition of the muriate; it is applied with a pencil, and burnished after it has been exposed to the heat of the porcelain furnace.

Many curious facts relating to the properties of gold and its uses in the arts, will be found in Dr. Lewis's Philosophical Commerce of the Arts.

SILVER.

620. Silver is found native, but in this state it is seldom pure, being mixed with small portions of other metals. This metal has been found in Cornwall and Devonshire, and mines of it exist in some parts of the European continent, but the richest known mines of this metal are those of Peru and Mexico.

621. To obtain it in a state of purity, we are ordered to dissolve the standard silver of commerce in pure nitric acid, diluted with an equal measure of water, and to immerse a plate of clean copper into the solution, which soon occasions a precipitate of metallic silver. This precipitate is to be well washed with distilled water, and then boiled for a short time in solution of pure ammonia.

622. Silver is of a pure white color, and of very brilliant lustre; it exceeds in malleability, and ductility, all the metals, with the exception of gold; it may be drawn into a wire finer than human hair. It is fusible at a bright red heat, and when in fusion is exceedingly brilliant.

623. It is not oxidised readily, even at a high temperature. The tarnish on silver is not merely oxidation, but, as shown by Proust, is occasioned by sulphureous vapors, and pure silver is not nearly so susceptible of it as that alloy of it with copper which is used for plate. An oxide of silver is produced by treating the metal with a powerful voltaic or electric influence. Pure water does not act upon the metal, but, when water is impregnated with animal or vegetable matter, a slight blackening of its surface takes place, owing to the presence of sulphur.

624. By adding lime water, or a solution of baryta, to a solution of nitrate of silver, and afterwards washing the precipitate, an oxide of the metal is obtained. This is of a dark olive color, and, is composed according to Sir H. Davy, of 100 parts of silver united with 7.3 oxygen. Mr. Faraday has made it probable that another combination of oxygen with silver exists in which the oxygen is in an inferior proportion; but this oxide does not seem capable of combining with acids.

625. Fulminating silver may be procured by treating the oxide of the metal with ammonia; and a detonating silver is formed by adding alcohol to a heated solution of silver in nitric acid. The first of these compounds detonates with a very gentle heat, and even by friction of the slightest

2 E

kind. The second requires a smart blow, or long continued friction, to occasion its detonation.

626. Silver combines with chlorine and forms a chloride of silver, which may be most easily obtained by adding a solution of nitrate of silver to one of common salt, (muriate of soda, or chloride of sodium;) a precipitate falls of a white color, which, upon exposure to the air, becomes brown, and ultimately black. When this chloride of silver is heated to dull redness, in a silver crucible, it fuses, and upon cooling concretes into a semi-transparent grayish substance, which is called luna-cornea, or horn silver.

627. Chloride of silver is very soluble in liquid ammonia; it also dissolves in hyposulphurous acid, and is decomposed by hydrogen gas; but hydrogen freed from all impurities, and directed upon moistened chloride of silver in the dark effects no change. Faraday, Journal of Science, viii. p. 375.

Chloride of silver is found native in some of the mines.

628. Iodide of silver may be formed by adding hydriodic acid to a solution of nitrate of silver. This is of a greenish-yellow color, and is not only insoluble in water, but also in liquid ammonia.

629. Sulphuret of silver.-The common tarnish of silver, as above intimated, is the formation of a sulphuret upon its surface. The sulphurets of the alkalis, and sulphureted hydrogen gas, precipitate silver from its solutions, and form sulphurets. Native sulphuret, or vitreous silver ore, occurs in various forms.

630. With phosphorus, silver forms a white brittle compound-a phosphuret of the metal. 631. Salts of silver. Chlorate of silver is obtained by digesting oxide of silver in chloric acid. It assumes the form of rhomboidal crystals.

632. Iodate of silver is precipitated in the form of a white powder, by adding iodic acid to the nitrate in solution. This is soluble in ammonia. 633. Sulphate of silver is formed by mixing nitrate of silver with sulphate of soda. It may be also procured by boiling silver in sulphuric acid. This salt appears in the form of needleshaped prismatic crystals.

634. Hypo-sulphite of silver may be formed by dropping a weak solution of nitrate of silver into a weak solution of hypo-sulphate of soda. The flavor of this salt is highly sweet, though composed of bitter ingredients.

635. Nitrate of silver.-Nitric acid diluted with about three parts of water dissolves silver readily, and nitric oxide gas is disengaged. If the silver used be pure, the solution will be colorless; if there be any mixture of copper, it will assume a greenish cast.

636. This solution when evaporated deposits large regular crystals, of a white color, which however blacken when exposed to the light. A

solution of the salt stains animal substances a

deep black; and, what is very curious, the salt itself when taken into the stomach in small quantities, as employed medicinally, occasionally produces a grayish tinge over the whole skin, which remains for a great length of time.

637. If the salt be heated in a silver crucible it fuses, and then, when cast into small cylinders, forms the lapis infernalis or lunar caustic of the

shops; the argenti nitras of the London Pharmacopoeia.

638. When mercury is introduced into the solution of nitrate of silver, a beautiful crystalline deposit is produced, which is called arbor Dianæ. Beaumé directs the following process in order to be successful with this experiment:- Mix together six parts of a solution of silver in nitric acid, and four of a solution of mercury in the same acid, both completely saturated. Add a small quantity of distilled water; and put the mixture into a conical glass, containing six parts of an amalgam made with seven parts of mercury and one of silver. At the end of some hours there appears on the surface of the amalgam a precipitate in the form of a vegetation.' Proust, however, tells us that nothing more is necessary to produce the arborisation, as beautiful as may be, than to throw mercury into nitrate of silver very considerably diluted."

639. Nitrate of silver is employed for writing upon linen, under the name of marking ink.

640. Phosphate of silver is formed by dropping a solution of phosphate of soda into nitrate of silver. This compound is used in preparing chloric acid.

641. Silver is capable of combining with most of the other metals. The standard silver of this country is an alloy with copper, in the proportion of 0.90 to 11:10. See Aikin's Chemical Dictionary, and Children's Translation of Thenard on Chemical Analysis.

PALLADIUM.

642. Dr. Wollaston directs the following pro

of platinum in nitro-muriatic acid, neutralised cess for obtaining palladium. Digest the ore by soda; separate the platinum by muriate of ammonia and filter. Then to the filtered liquor let a solution of cyanuret of mercury be added. A flocculent precipitate is gradually formed, yields palladium upon exposure to heat. which is prussiate of palladium, and which

643. Palladium is of a dull white color, it is malleable and ductile. It requires for its fusion a temperature above that required for the fusion of gold. Muriatic acid, by being boiled upon this metal, acquires a beautiful red color. With sulphuric acid a blue color is produced. Nitric acid acts with more energy upon it, than either the sulphuric or muriatic; but its best solvent is the nitro-muriatic acid; and from all the solutions of the metal in the acids, alkalis and earths will produce precipitates. Palladium combines with sulphur, with potassa, and with the other metals. Like platinum, palladium destroys the color of gold, even when mixed with it in very small proportions. Dr. Wollaston has furnished an alloy of gold and palladium for the gradua tion of the magnificent circular instrument, constructed by Mr. Troughton for the Greenwich observatory. It has the appearance of platinum, and a degree of hardness which peculiarly fits it for receiving the graduations. Henry.

MERCURY.

644. This, as we have before stated, is the only known metal that is fluid at the ordinary temperature of the atmosphere; and it requires for its solidity that the temperature be reduced to

about 40° below zero of Fahrenheit. At about 660° it boils and is converted into vapor.

645. This metal has been known from a very early period. It was named quicksilver from its semi-fluidity, joined with its white silvery appearance. It is occasionally adulterated by a mixture of lead or bismuth; but it is not then so fluid as when pure. The native metal occurs in small fluid globules, in most of the mines which produce the ores of this metal.

646. Oxides of mercury.-Oxygen combines with mercury in two proportions, forming the black oxide or protoxide of the metal, which may be obtained by long agitation of it in contact with oxygen, or by washing calomel with hot lime water, or by boiling calomel with strong solutions of potassa or soda. This was named by Boerhaave, Ethiops per se. It exists in the pilula hydrargyri, and in the mercurial ointment of the Pharmacopoeia.

647. The other or red oxide or peroxide of mercury is produced by exposing the fluid metal, at a high temperature, for several days to the action of oxygen. This oxide was formerly called precipitate per se, or calcined mercury, and is the hydrargyri oxidum rubrum of the Pharmacopia. This is said to be composed of 100 metal, and 8 of oxygen, while the black oxide contains just half the proportion of oxygen.

648. Peroxide of mercury is decomposed if exposed to the light for a length of time. It is soluble in water, and with ammonia forms an ammoniuret, which is decomposed by heat.

649. Mercury and chlorine.-These combine in two proportions, forming the chlorine or bichloride, and the proto-chloride (calomel). These compounds are usually named corrosive sublimate, and calomel. As these salts are preparations of much interest and importance, we shall take the liberty of extracting from Mr. Brandes' Manual, his remarks on their formation and properties.

650. Corrosive sublimate, or bi-chloride, or, as Mr. Brande calls it, perchloride, may be obtained, says he, by a variety of processes.

651. When mercury is heated in chlorine, it burns with a pale flame; the gas is absorbed, and a white volatile substance rises, which is the perchloride.

652. It may also be obtained by dissolving peroxide of mercury in muriatic acid, evaporating to dryness, re-dissolving in water, and crystallising.

653. The ordinary process for making corrosive sublimate, consists in exposing a mixture of chloride of sodium (common salt), and per-sulphate of mercury, to heat in a flask, or other proper subliming vessel, a mutual decomposition ensues. The chlorine of the common salt unites to the mercury of the sulphate, and forms bichloride of mercury. The oxygen of the oxide of mercury converts the sodium of the salt into soda, which, with the sulphuric acid, produces sulphate of soda. This decomposition is exhibited in the following diagram :

advantage in washing calomel, to free it from corrosive sublimate.

omit them.

654. Perchloride of mercury is usually seen in the form of a perfectly white, semi-transparent mass, exhibiting the appearance of imperfect crystallisation. It is sometimes procured in quadrangular prisms. Its taste is acrid and nauseous, and leaves a peculiar metallic and astringent flavor upon the tongue. It dissolves in twenty parts of water at 60°, and in about half its weight at 212°. It is more soluble in alcohol than in water. When heated it readily sublimes in the form of a dense white vapor, strongly affecting the nose and mouth. It dissolves without decomposition in muriatic, nitric, and sulphuric acids; the alkalis and several of the metals decompose it. It produces, with muriate of ammonia, a very soluble compound; hence a solution of sal-ammoniac is used with

655. The compound commonly termed calomel (proto-chloride of mercury), was first mentioned by Crollius, early in the seventeenth century. The first directions for its preparation are given by Beguin in the Tyrocinium Chemicum, published in 1608. He calls it draco mitigatus. Several other fanciful names have been applied to it, such as aquila mitigata, manna metallorum, panchymagogum minerale, sublimatum dulce, mercurius dulcis, &c.

656. The most usual mode of preparing calomel consists in triturating two parts of corrosive sublimate with one of mercury, until the globules disappear, and the whole assumes the appearance of an homogenous gray powder, which is introduced into a matrass, placed in a sand heat, and gradually raised to redness. The calomel sublimes, mixed with a little corrosive sublimate, the greater part of which, however, being more volatile than the calomel, rises higher in the matrass; that which adheres to the calomel may be separated by reducing the whole to a